In a print process of an image forming apparatus employing an electrographic system, a method for executing a discharging (waste) process of a toner (deteriorated toner) in a development device by comparing the printing rate in a period until the number of rotations of a photosensitive drum as a image carrier reaches a predetermined number of rotations (corresponds to the number of print dots) and a threshold value is proposed (for example, see Patent Document 1).